Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 300837
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
337 AM CDT TUE AUG 30 2016

.TODAY AND TONIGHT...Forecast Confidence Is Medium.

Band of showers and storms sagging south through nw WI and east-
central MN ahead of pre-frontal surface trough in region of weak 925
and 850 mb frontogenesis and differential CVA ahead of a vorticity
maximum south of main short wave trough tracking east across nrn
Ontario. The strongest cells in east-central MN are riding the
outflow boundary south-southwest along corridor of richer lower-
level moisture pooling ahead of the 925 mb trough within a pocket of
modest mid-level lapse rates around 7C/km. The showers/storms to the
east are diminishing as outflow races out ahead with only an
isolated shower or storm quickly popping up and dying along the
boundary.

Other showers and storms are re-firing over northern Illinois ahead
of a weak vort max/MCV within region of nearly stationary moisture
convergence and moving east just south of the border. A few light
showers within region of differential CVA with this feature are
crossing western sections of the CWA.

Will have slight chance/low chance PoPs in the southern forecast
area this morning to account for the potential of the southern band
of showers/storms in IL slipping into southern WI. Then chance PoPs
this afternoon with the weak forcing along the cold front, tapering
off from northwest to southeast this evening as the front moves
through. Could see some gusty north-northeast winds along the lake
as hi-res models indicate the front moving a bit faster down the
lake versus inland, with a brief period of 15 to 20 knot winds
within 1k ft of the surface right behind the front.

.WEDNESDAY THROUGH FRIDAY - Confidence...Medium to High
Cold advection regime sets up Wednesday into Thursday as low
level thermal trough becomes established across the area. We will
be situated on western side of evolving mid/upper level
trough across the NE US. The NAM and GEM are more pronounced with
a glancing shortwave riding sewd in this flow while the GFS and
ECMWF keep this wave further east. 925 temps will settle into the
low to mid teens celsius. So a much cooler and more comfortable/drier
airmass this period. The mid level ridge axis starts to slide
across WI on Friday.

.SATURDAY - Confidence...Medium to High
The surface high shifts well to the east though the expansive
anticyclonic influence lingers into srn WI. So another quiet day in
the works. The mid level ridge shifts east as well so we start to
see a more southwest flow at 500 millibars. The 925 temps bounce
back a bit due to a switch to a more southerly low level
trajectory.

.SUNDAY - Confidence...Medium
The southerly low level flow strengthens further with 925 temps
rising into the low 20s celsius. The 500 millibar flow remains
southwest with the GFS is a bit more robust on the shortwave
activity riding through. Other models are weaker with this feature
and with a track more to our northwest. Primary cyclogenesis and
frontal convergence remains well to our west. While core of
strongest 850 jet remains across IA/ern MN and nw WI there is an
eastward extension of this jet with some moist advection and the
wave that suggests the Superblend pops are onto something for our
western CWA so will leave them as is for now.

.LABOR DAY - Confidence...Low
Differences arise with the GFS building ridge axis north keeping
things less progressive on the shortwave energy front. meanwhile the
ECMWF shows things moving along with frontal system and band of
convection. The GFS implies a more east/west oriented frontal
boundary laying across central WI with still some convective chances
here but this scenario would suggest more scattered activity while
the ECMWF solution shows more widespread shra/tsra with the cold
frontal passage. Given the range of solutions will stick with the
Superblend guidance for now.

&&

.AVIATION/12Z TAFS/...Mid level cloud deck has limited extent of fog
coverage overnight and have adjusted TAFs for a more optimistic vsby
forecast in the near term. Mainly VFR conditions expected through
the forecast, though expect scattered showers and storms to develop
along a weak cold front this afternoon and evening, pushing southeast
of the forecast area between 09Z and 12Z Wednesday. Will keep pcpn
mention as vicinity for now, though MVFR cigs/vsbys with any
showers/storms that reach TAF sites. Looking for a brief period of
gusty north to northeast winds at far eastern locations with cold
front moving a bit faster down Lake Michigan versus inland, with a
brief period of 15 to 20 knot winds within 1k ft of the surface
right behind the front.

&&

.MARINE...Looking at potential of a few showers or thunderstorms
slipping north into the southern marine zones this morning, but
scattered showers and storms will hold off until this afternoon
and evening as a cold front drops through the region. Looking for
a brief period of gusty north to northeast winds with cold front
moving a bit faster down Lake Michigan versus inland, with a brief
period of 15 to 20 knot winds within 1k ft of the surface right
behind the front. This will build wave heights to 2 to 4 feet by
Wednesday morning. North winds and waves will approach Small Craft
Advisory levels Wednesday into Wednesday night.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$
TODAY/TONIGHT AND AVIATION/MARINE...REM
Wednesday THROUGH Monday...Collar


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